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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.asynchronous_socket_operations"></a><a class="link" href="asynchronous_socket_operations.html" title="Requirements on asynchronous socket operations">Requirements
      on asynchronous socket operations</a>
</h3></div></div></div>
<p>
        In this library, <span class="emphasis"><em>asynchronous socket operations</em></span> are
        those member functions having prefix <code class="computeroutput">async_</code>.
      </p>
<p>
        For an object <code class="computeroutput">s</code>, a program may initiate asynchronous socket
        operations such that there are multiple simultaneously outstanding asynchronous
        operations.
      </p>
<p>
        When there are multiple outstanding asynchronous <a class="link" href="read_write_operations.html" title="Requirements on read and write operations">read
        operations</a> on <code class="computeroutput">s</code>:
      </p>
<p>
        — having no argument <code class="computeroutput">flags</code> of type <code class="computeroutput">socket_base::message_flags</code>,
        or
      </p>
<p>
        — having an argument <code class="computeroutput">flags</code> of type <code class="computeroutput">socket_base::message_flags</code>
        but where <code class="computeroutput">(flags &amp; socket_base::message_out_of_band) == 0</code>
      </p>
<p>
        then the <code class="computeroutput">buffers</code> are filled in the order in which these operations
        were issued. The order of invocation of the completion handlers for these
        operations is unspecified.
      </p>
<p>
        When there are multiple outstanding asynchronous <a class="link" href="read_write_operations.html" title="Requirements on read and write operations">read
        operations</a> on <code class="computeroutput">s</code> having an argument <code class="computeroutput">flags</code>
        of type <code class="computeroutput">socket_base::message_flags</code> where <code class="computeroutput">(flags &amp;
        socket_base::message_out_of_band) != 0</code> then the <code class="computeroutput">buffers</code>
        are filled in the order in which these operations were issued.
      </p>
<p>
        When there are multiple outstanding asynchronous <a class="link" href="read_write_operations.html" title="Requirements on read and write operations">write
        operations</a> on <code class="computeroutput">s</code>, the <code class="computeroutput">buffers</code> are transmitted
        in the order in which these operations were issued. The order of invocation
        of the completion handlers for these operations is unspecified.
      </p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2021 Christopher
      M. Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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